1. Field of the Invention
The present invention relates to a novel pressure-sensitive transferring protective covering material which enables to prevent a print formed of a dye, particularly, a print formed by means of an ink jet system using a dye from being deteriorated by light. More particularly, the present invention relates to a novel pressure-sensitive transferring protective covering material in the form of a film, which can be used in a manner of transferring it onto an object having a print formed of a dye thereon so that the print is prevented from being deteriorated by light. The present invention also relates to a method for protecting and covering a print formed of a dye on an object using said pressure-sensitive transferring protective covering material, whereby preventing the print from being deteriorated by light.
2. Related Background Art
It is known that dyes used for ink jet printing are insufficient in terms of light fastness, and as for a print formed on a so-called ink jet printing paper comprising a coated paper having a pigment-containing coat disposed on a base paper by way of ink jet printing using such dye, though the print is good enough in quality, it is insufficient in light stability or fade resistance and because of this, it is liable to gradually fade or discolor after some time. This is due to the fact that a cationic functional group-bearing cationic polymer as a water proof agent is usually contained in the coat of the ink jet printing paper for the purpose of fixing a dye in the coat. Particularly, the cationic functional group of such cationic polymer provides a negative effect for the release of an energy generated as a result of photo reaction and because of this, the cationic polymer is liable to reduce the light resistance of the dye.
In order to eliminate these problems, U.S. Pat. Nos. 4,926,190, 5,089,050, 5,124,723, and 5,261,953 propose various light stabilizers for use in inks or printing papers for ink jet printing.
According to the specifications of these U.S. patents, it is understood that the use of these light stabilizers provides a reasonable effect in terms of stabilization against light. However, the extent of the effect provided by such stabilizer is not of a satisfactory level in comparison with a light stabilization effect provided in the case of using a conventional printing ink.
The reasons for this can be considered as will be described below.
(1) In general, in the case where a light stabilizer is contained in a printing paper, a dye applied to the printing paper substantially remains on the surface thereof and because of this, only a part of the amount of the stabilizer effects the dye. In addition, the light stabilizer added is substantially present in the printing paper and because of this, it does not function as a filter while remaining on the surface of the printing paper.
(2) Further, in the case where a light stabilizer is contained in an aqueous ink, as the light stabilizer is usually not high in solubility against the aqueous ink, and even in the case where it should be resolved in the aqueous ink, and therefore, as for the light stabilizer, there is a limit in terms of compatibility with other components of the ink. Because of this, the light stabilizer which comes to effectively work on the surface of a printing paper is not of a sufficient rate in comparison with the amount of the light stabilizer added.
For these reasons, only several of the light stabilizers disclosed in the above U.S. patent documents have been practically used in inks or printing papers for ink jet printing.
Separately, in order to improve the light stability of a print formed with a dye on a printing paper, there has been proposed a method of covering the print by a protective material film, wherein the protective material film is superposed on the print-bearing surface of the printing paper so as to cover the print. According to this method, there can be attained a certain improvement in the fastness of the print and also in the texture of the printing paper. As such protective material film, various protective material films are commercially available.
However, as for this method, there are problems such that as the protective material film itself is laminated directly on the print, the texture of the printing paper is liable to undesirably change and in addition to this, the method is still insufficient in order to improve the light resistance of the print.